Recently, coloring of solid state image sensing devices (which are being heralded as the image sensing devices of the next generation, taking the place of electron tubes and image sensing tubes) is being performed by forming a color filter in the upper part of a photoelectric conversion region. Similarly, the coloring of a display device such as a liquid crystal display device is being performed by forming a color filter in the upper part of a photoelectric conversion region.
The kinds of color filters are classified into an organic filter colored with organic matter such as gelatin or with another coloring agent, and an inorganic filter which uses optical interference. Among the filters mentioned above, the organic filter is more widely used than the inorganic filter due to its lower cost.
FIG. 1 is a cross sectional drawing illustrating a color filter for a prior art Charge Coupled Device (CCD). In FIG. 1, the silicon substrate 1 whose surface is concave and convex, has photo diode arrays 2,3,4 formed at the surface of the concave region, and a conducting layer 5 and an insulating layer 6 formed at the surface of the convex region.
Among the conducting layers 5, a section is used in pad for the electrical connection between the semiconductor device and the package, and the insulating layers 6 are used in the electrical insulation of the photo diode arrays 2,3,4.
The manufacturing process for the embodiment of the above-mentioned structure is explained briefly as follows. In the silicon substrate 1 whose surface is concave and convex, photo diode arrays 2,3,4 are formed at the surface of the concave region, and a conducting layer 5 and an insulating layer 6 are formed at the surface of the convex region. A planarizing layer 7 is applied on the surface of the silicon substrate 1 by a transparent agent such as a polyimide.
Thereafter, a photosensitive agent such as casein or gelatin mixed with ammonium dichromate is applied in the upper region of the planarizing layer 7 and a color filter pattern 8 is formed by photo lithography.
Next, a coloring agent is applied in the planarizing layer 7 and the color filter pattern 8. Then, a coloring layer 9 is formed by coloring only the color filter pattern 8. The coloring layer 9 is colored with any one of the coloring agents such as magenta, cyan or yellow in order to filter any one of the colored lights magenta, cyan or yellow.
Thereafter, a medium layer 11 is formed by applying polyimide at the surface of the above-mentioned structure. In a manner similar to that outlined above, color filter patterns 13, 19, and coloring layers 15, 21, which can filter the respective desired color at the surface of the color filter patterns 13, 19 and the medium layers 11 and 17, are formed. The medium layers 11, 17 prevent the coloring layers from being mixed with each other. Next, a protective layer 23 is formed over the entire surface of the above-mentioned structure by applying polyimide, and a portion of the pad 5 is then exposed by forming an opening 25 for an electrode.
Another prior color filter is shown in Republic of Korea Patent Publication 83-1454. The color filter therein described has the problem that its picture quality is inferior due to the dispersion phenomena brought about by the diffraction and reflectance of incident light. Picture quality is also degraded by the reduction of optical transmittance by the medium layers, as the color filter layers corresponding to the photoelectric cell arrays are formed at respectively different heights and the medium layers are thickened upon being laminated. The prior art device also has difficulty in fashioning the opening for the electrode.